mb/hp/elitebook_820_g2: do not set EC SLPT on S5

Setting EC SLPT bit in S5 will make HP EliteBook 820 G2
fail to reboot under Linux 6.1 and later kernel versions.

Change-Id: I48f5a35cd78db3b32d9f76cb8e266c738da34e7c
Signed-off-by: Iru Cai <mytbk920423@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/78907
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Felix Singer <service+coreboot-gerrit@felixsinger.de>

src/mainboard/hp/elitebook_820_g2/acpi/platform.asl

@@ -9,6 +9,9 @@ Method(_WAK,1)
 }
 
 Method(_PTS,1)
+{
+	If (Arg0 != 5)
 	{
 		\_SB.PCI0.LPCB.EC0.SLPT = Arg0
 	}
+}